Relative Partial Cross Sections for Single, Double, and Triple Photoionization of C60 and C70
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- 作者：Koichiro Mitsuke ; Hideki Katayanagi ; Bhim P. Kafle ; Chaoqun Huang ; Hajime Yagi ; Md. Serajul I. Prodhan ; Yoshihiro Kubozono
- 刊名：Journal of Physical Chemistry A
- 出版年：2007
- 出版时间：August 30, 2007
- 年：2007
- 卷：111
- 期：34
- 页码：8336 - 8343
- 全文大小：360K
- 年卷期：v.111,no.34(August 30, 2007)
- ISSN：1520-5215
文摘
Partial cross sections for the photoion formation from C60 and C70 were determined from the yields of singly,doubly, and triply charged ions which were measured by mass spectrometry combined with tunable synchrotronradiation at h
= 25-120 eV. The dependence of the detection efficiencies on the mass-to-charge ratio wasevaluated by using the formula proposed by Twerenbold et al. Corrections of the detection efficiency werefound to be critical for obtaining accurate partial cross sections for photoionization of fullerenes. Revisionswere made of the partial cross-section curves for single and double photoionization of C60 and C70. The curvefor triple photoionization of C70 was newly proposed. The ratios between the cross sections for double andsingle photoionization increase with h and reach saturated values of 0.78 at 85 eV for C60 and ~1.3 at 100eV for C70. In contrast, the ratios at 120 eV between the cross sections for triple and single photoionizationof C60 and C70 amount to 0.14 and ~0.38, respectively. The formation mechanism of multiply charged fullereneions was discussed in terms of valence-electron excitation to antibonding unoccupied orbitals and/or sphericalstanding waves inside the cavity of a fullerene. This excitation could be followed by Spectator Auger processesand transmission of the excess electronic energy among numerous vibrational degrees of freedom.
= 25-120 eV. The dependence of the detection efficiencies on the mass-to-charge ratio wasevaluated by using the formula proposed by Twerenbold et al. Corrections of the detection efficiency werefound to be critical for obtaining accurate partial cross sections for photoionization of fullerenes. Revisionswere made of the partial cross-section curves for single and double photoionization of C60 and C70. The curvefor triple photoionization of C70 was newly proposed. The ratios between the cross sections for double andsingle photoionization increase with h and reach saturated values of 0.78 at 85 eV for C60 and ~1.3 at 100eV for C70. In contrast, the ratios at 120 eV between the cross sections for triple and single photoionizationof C60 and C70 amount to 0.14 and ~0.38, respectively. The formation mechanism of multiply charged fullereneions was discussed in terms of valence-electron excitation to antibonding unoccupied orbitals and/or sphericalstanding waves inside the cavity of a fullerene. This excitation could be followed by Spectator Auger processesand transmission of the excess electronic energy among numerous vibrational degrees of freedom.